Because their wide spectral characteristics allow a user to transport broadband signals, and offer considerable flexibility in the choice of data rates for serialized digital data, fiber optic (digital) communication systems are now preferred over and are being installed to replace a variety of conventional metallic cable networks. However, at relatively high data rates (e.g. those above several hundred Mb/s to one Gb/s or higher), the limited performance capabilities of readily available and reduced cost electronic circuits and components has limited the end-to-end link distance (of what is commonly referred to in the communications industry as "(802.3 z) Gigabit Ethernet") to essentially that of a local area network, covering a distance of on the order of 5 km or less.
Where transport over long haul distances (considerably in excess of 5 km) is desired, it has been customary practice to require a signal protocol conversion (e.g., from Ethernet to a synchronous optical network (SONET) based system), which is cost-prohibitive to most LAN customers. Still, as telecommunication customers are increasingly relying upon the rapid information access and transport capabilities of digital communication networks, it has become apparent to many if not most service providers of the need to extend the range of high speed data communications to distances well beyond that of local area network, but in a manner that is both transparent and cost acceptable to the end user.